Waste materials ("oily sludge") from oil refineries, drilling operations, and other chemical and industrial operations may contain particulates of different physical and chemical compositions, hydrophobic oil fractions and water. The particulates themselves are generally hydrophilic minerals, but may include some hydrophobic particulates. "Hydrophobic oil" generally includes hydrocarbon oil and hydrophobic organic compounds with alkyl, aryl, or alkyl-aryl groups. "Oil" as used herein includes materials that are generally hydrophobic, not only petroleum or petroleum-based substances, but also oils derived from plants and vegetables.
Solid-liquid separation processes have been used to remove solids from liquid phases with varying degrees of success. Currently, industry uses expensive filtration and centrifuge operations as well as heat and chemical treatments to treat oily sludge and other waste materials. A major problem industry is facing, however, is the separation of hydrophobic oil from oily sludge. More specifically, how to liberate oil from the surfaces of the solid particles, especially where the oil has to some extent been adsorbed.
It is known that various screening systems are useful to separate solid particulates based on size differentials. Also, in some instances water rinsing can be used to remove oil from coarse particles; however, rinsing generally does not remove oil from fine particulate solids where there is significant adsorption.
Existing filtration and centrifuge processes accompanied by heat and chemical treatments can reduce the oil content of the solid particulates to a certain extent. But filtration and centrifuge operations are relatively expensive unit processes. Moreover, heat and chemical treatments have a further adverse influence on the economics of the operation. Therefore, it is an object of this invention to develop alternative processes which can either replace or complement the aforementioned processes for the treatment of oily sludge.